This protocol investigates the importance of steroid feedback on CRH release from the hypothalamus and on ACTH release from the anterior pituitary. With an infusion of cortisol, at a time when endogenous CRH drive is high, we found fast feedback effect of cortisol on beta-endorphin and ACTH secretion in normal subjects. Using metyrapone in the late afternoon/evening, we are able to block cortisol secretion with rebound effects on ACTH and beta-endorphine secretion.